The invention relates generally to welding systems, and, more particularly, to circuits for controlling the inrush of current into certain welding devices upon connection and/or power-up.
Various types of welding systems and components have been developed for joining metal workpieces throughout all areas of industry. Many such systems rely upon remote wire feeders and pendants that may be located some distance from a power supply that provides the power needed for welding operations. Wire feeders, for example, server to provide a flow of welding wire for metal inert gas (MIG), flux cord wire welding, and similar operations. The wire feeders may allow some degree of control of the welding operation settings, and may permit pass through of power for other types of welding. They can conveniently be positioned some distance from the welding power source, such as close to the actual location of the workpiece. This is particularly convenient for applications such as construction, ship building, boiler and plant work, and so forth. Pendants, similarly may be positioned at some distance from a welding power supply, and differ from wire feeders in several respects. For example, they may be used to control or alter weld settings, while not providing a flow of welding wire. Such pendants are particularly useful in situations where the welding operation is performed at some distance from the power source, thereby allowing some degree of control over the welding process without the need to return to the power source.
Increasingly, remote wire feeders and pendants are required to include capacitive circuits for enabling initialization of welding operations, powering of the component, and ride-through of certain power events that may occur before, during and after welding. For example, pendants may be used for stick and tungsten inert gas (TIG) welding. In certain of these, initiation of the welding arc may require capacitive circuits for storing initiation power for initiation of the arc. Wire feeders, also, may require stored energy for powering their control, particularly during certain phases of operation. If such capacitive circuit-equipped components are connect for the first time to a “live voltage source”, a substantial amount of current may flow through the connection to charge the capacitive circuit. This can result in a spark or arc as the connection is made. It may be advantageous to avoid such arcing by controlling the inrush of current to the component from the live power source. Similarly, accessory devices (e.g., wire feeders, operator remote interfaces, etc.) that are powered by a weld cable voltage require some form of local energy storage element to allow them to continue functioning during inevitable, though temporary, short circuit conditions seen when touching an electrode to a workpiece (i.e., arc start). The storage element should not be allowed to draw current at a level that would starve the accessory device and therefore may require a current limiter of some sort.